Today I will show how to get SPList Items by filtering using CAML query. Also this post includes how to get the data from a custom field.
I use JQuery.Deferred and Promise in order to achieve the success and failure of the asynchronous call. There are plenty of articles on the internet regarding JQuery.Deferred. Please see the Reference section for more on this.
Should say Melick (http://melick-rajee.blogspot.com) for the guide on SharePoint Apps.